The present invention relates to continuous filament nonwoven webs.
There exist a variety of processes for forming continuous filament nonwoven webs. The spunbond fiber process is one example. Generally speaking, methods for making spunbond fiber nonwoven webs include extruding molten thermoplastic polymer through a spinneret and drawing the extruded polymer into filaments to form a web of randomly arrayed fibers on a collecting surface. As examples, methods for making the spunbond fiber webs are described in U.S. Pat. No. 4,692,618 to Dorschner et al., U.S. Pat. No. 4,340,563 to Appel et al. and U.S. Pat. No. 3,802,817 to Matsuki et al. A second and distinct process for making continuous filament nonwoven webs is the meltblowing process. Meltblown fiber webs are generally formed by extruding a molten thermoplastic material through a plurality of fine die capillaries as molten threads or filaments into converging high velocity air streams which attenuate the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Meltblown fiber processes are disclosed in, by way of example only, U.S. Pat. No. 3,849,241 to Butin et al., U.S. Pat. No. 5,160,746 to Dodge et al. and U.S. Pat. No. 4,526,733 to Lau.
Continuous filament nonwoven webs have found industrial applicability in a wide range of products and/or uses. As examples, continuous filament nonwoven webs have heretofore been used as filtration and/or barrier type materials such as in facemasks, sterilization wraps, HVAC media, surgical gowns, industrial workwear and so forth. Additionally, continuous filament nonwoven webs have been widely used as one or more components of personal care products. As examples, continuous filament nonwoven webs have been used in a variety of components ranging from liquid distribution layers, composite absorbent materials, baffles, coverstock and so forth. However, while continuous filament nonwovens have found wide acceptance within various industries the demands upon the physical attributes and/or performance of existing materials continues to increase. In addition, by improving the physical attributes and/or performance of continuous filament nonwoven materials the materials can be utilized in still a wider array of applications and products.
Thus, there exists a need for continuous filament nonwoven webs having improved and/or specialized physical attributes and functionality. More particularly, there exists a need for specialized continuous filament nonwoven webs having improved liquid handling properties, treatment retention and location, hand (i.e. softness), resiliency, durability, stretch-recovery and/or other desirable properties.
The aforesaid needs are fulfilled and the problems experienced by those skilled in the art overcome by nonwoven webs of the present invention comprising a unitary continuous filament nonwoven web comprising a composite of at least first and second continuous filaments. In one aspect of the present invention, the continuous filament nonwoven web comprises a blend or mixture of first continuous filaments and second continuous filaments wherein the second continuous filaments are different from the first continuous filaments. Desirably the second continuous filaments are substantially surrounded by the first continuous filaments.
In a further aspect, composite nonwoven webs of the present invention can comprise first and second continuous filaments that extend substantially in the machine direction and wherein the first continuous filaments comprise multicomponent filaments and the second continuous filaments comprise monocomponent filaments. The first continuous filaments can comprise at least about 50% of said composite nonwoven web and can also have an average denier less than that of the said first continuous filaments. The composite nonwoven web can also be through air bonded and have autogenous interfiber bonds. Further, the second continuous filaments can, in one aspect, comprise from about 10% to about 40% of the composite nonwoven web. Still further, first continuous filaments and second continuous filaments desirably have a denier ratio of not less than about 2:1. The first continuous filaments can be crimped or uncrimped filaments. In addition, the polymer composition comprising one of the components within the first continuous filaments desirably has a melting point at least 10xc2x0 C. below that of the polymer composition comprising the other components therein as well as the polymer composition comprising the second continuous filaments. As a particular example, the first continuous filaments can comprise polypropylene/polyethylene bicomponent filaments and the second continuous filaments can comprise polypropylene. The composite nonwoven web can, optionally, be treated so as to form an electret.
In still a further aspect of the invention, composite nonwoven webs of the present invention can comprise first continuous filaments and second continuous filaments extending substantially in the machine direction and that have different surface properties from one another and wherein the ratio of first continuous filaments to second continuous filaments is at least about 2:1. Desirably only one of said first and second continuous filaments contain an effective amount of an active agent selected from the group consisting of wetting agents, anti-static agents, alcohol repellency agents, odor-control agents, electret stabilizing agents, and so forth. The second filaments can, in one aspect, have a larger average denier than said first continuous filaments. Further, the first and second filaments can comprise either multicomponent filaments or monocomponent filaments. Either the first and/or second continuous filaments can be shaped filaments, i.e. having a non-round cross-section.